New Research Identifies a Possible Finite Number of Viruses

EcoHealth Alliance, a nonprofit organization that focuses on local conservation and global health issues, and the Center for Infection and Immunity (CII) at Columbia University's Mailman School of Public Health announced a new strategy to identify the total number of wildlife viruses that could potentially cause emerging disease outbreaks that threaten both public and wildlife health.

Combining field investigations with a new statistical approach, scientists estimate that there may exist a minimum of 320,000 viruses awaiting discovery from mammals alone. With over three-quarters of the emerging infectious diseases originating from wildlife this research gives scientists an estimate of the number of viral agents that may eventually cause a pandemic. Diseases such as SARS, West Nile virus, HIV/AIDS, Ebola and avian influenza are all examples of a zoonotic diseases – those that originate in wildlife and are spread to humans.

"For decades, we've faced the threat of future pandemics without knowing how many viruses are lurking in the environment, in wildlife, waiting to emerge. Finally we have a breakthrough – there aren't millions of unknown virus, just a few hundred thousand, and given the technology we have it's possible that in my lifetime, we'll know the identity of every unknown virus on the planet," says Peter Daszak, PhD, corresponding author and president of EcoHealth Alliance.

Emerging disease outbreaks cause both social concerns and economic problems. The threat alone of a new emerging disease such as the newly discovered Middle East Respiratory Syndrome (MERS) can directly affect the economic stability of the global economy. Economic losses due to the SARS outbreak was estimated to be anywhere from $15 billion to more than $50 billion. Scientists in this new study worked to establish a quantifiable cost to the discovery of these 320,000 new viruses: $1.2 million for one host species such as the Indian flying fox bat or a total of $6.3 billion for all mammals. The cost of discovering these viruses is a fraction of the cost required to respond to a global pandemic like H1N1 influenza or SARS. Given the disproportionate cost of discovering the rarest of the rare, scientists showed that limiting efforts to 85 percent of estimated viral diversity would bring the cost down to $1.4 billion.

"Historically, our whole approach to discovery has been altogether too random," says lead author Simon Anthony, D.Phil, a scientist at the Center for Infection and Immunity (CII) at Columbia University's Mailman School of Public Health. "What we currently know about viruses is very much biased towards those that have already spilled over into humans or animals and emerged as diseases. But the pool of all viruses in wildlife, including many potential threats to humans, is actually much deeper. A more systematic, multidisciplinary, and One Health framework is needed if we are to understand what drives and controls viral diversity and following that, what causes viruses to emerge as disease-causing pathogens."

EcoHealth Alliance scientists continue to work on the frontlines of viral discovery in emerging disease hotspots regions around the world focused at the intersection of the environment, health, and capacity building. EcoHealth Alliance is focused on understanding the environmental drivers of zoonotic disease emergence and promoting the conservation of all species.

"PREDICT has already discovered more than 240 novel viruses throughout the world in areas where people and animals live in close contact and depend on the same natural resources," says study co-author Jonna Mazet, PhD, director of the UC Davis One Health Institute and co-director of PREDICT. "That includes new coronaviruses, like the ones that cause SARS and the new Middle East Respiratory Syndrome."

The current study is the result of a multidisciplinary collaboration between 21 molecular virologists, ecologists, veterinarians, and mathematicians from institutions, including the Center for Infection and Immunity at Columbia's Mailman School; EcoHealth Alliance, National Autonomous University of Mexico, University of California Davis; International Centre for Diarrhoeal Disease Research, Dhaka (Bangladesh); Princeton University; National Institutes of Health; and Chittagong Veterinary and Animal Sciences University (Bangladesh).

"To quote Benjamin Franklin, an ounce of prevention is worth a pound of cure," says W. Ian Lipkin, MD, director of CII. "Our goal is to provide the viral intelligence needed for the global public health community to anticipate and respond to the continuous challenge of emerging infectious diseases." The study, titled "A strategy to estimate unknown viral diversity in mammals," appears in the journal mBio. Support for the research was provided by United States Agency for International Development (USAID) and the PREDICT Project.